Gear pump



United States Patent O 3,435,773 GEAR PUMP Berth Ulrik Gustafsson, Saffle, Sweden, assignor to AB Kalle-Regulatorer, Sallie, Sweden Filed Aug. 23, 1967, Ser. No. 662,747 Claims priority, application Sweden, Sept. 28, 1966, 13,077/ 66 Int. Cl. F04c 1/04; F04!) 13/02, 19/06 US. Cl. 103-126 Claims ABSTRACT OF THE DISCLOSURE A gear pump system comprising two gear wheels in engagement with an intermediate central wheel to form two pump units each having inlets for gas and liquid located such that the pump units will operate independent of each other.

BACKGROUND OF THE INVENTION Field of the invention The invention relates to a gear pump, particularly adapted to be used for operating hydraulic regulators.

Description of the prior art In certain hydraulically operating regulators it is known to use a gear pump having inlets for gas and liquid on its suction side, while the pressure side of the pump communicates with a restricted outlet as well as a conduit adapted to be connected to a hydraulic cylinder.

SUMMARY OF THE INVENTION The invention relates to gear pumps of this type and has particularity for its object to provide a device capable of replacing two separate pump units of the known design. For that purpose, two gear wheels are in engagement with an intermediate central gear wheel in a housing to form two pump units each having an outlet from its pressure chamber. Further, inlets for gas and liquid are provided on both sides of each pressure chamber at a distance of at least two gear pitches from the pressure chamber as well as from the central portion of the suction side. B-y such a location of the inlets, the two pump units will operate entirely independent of each other in spite of the fact that the central wheel is common to both pumps. If the fluids were supplied centrally on the suction sides, as is the case in the known gear pumps, they would pass around the periphery of both cooperating wheels onto both pressure chambers, so that the three gear wheels would function as a single pump. A distance of two gear pitches, however, provides for an effective seal against such a communication. By providing inlets for gas and liquid on both sides of each pressure chamber the capacity of the pump units will be entirely utilized in that the gaps between the teeth of the three wheels are always filled up with fluid.

If desired, the new pump device may be used for operation of two different regulators, but especially it will be valuable for a regulator which uses two pumps driven at the same speed, in that the expensive transmissions between the two separate pumps and a common motor are eliminated. In the new pump device only one of the wheels must be driven, and preferably the central wheel may thus be mounted directly on the driving shaft of a motor. In a double-acting regulator of the type described in the Swedish Patent No. 194,307, for instance, each pump unit may, of course, be arranged to operate one of two cooperating hydraulic cylinders, but a more simple construction is obtained, if said units are connected each to one end of a common servo cylinder.

Patented Apr. 1, 1969 BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENT A housing 1 encloses three gear wheels 2, 3, 4 mounted radially in alignment in such a way that the intermediate wheel 3 is in engagement with each of the two outer Wheels 2 and 4. The central wheel 3 is assumed to be driven in counter clockwise direction by a motor, not shown, and the two other wheels 2, 4 will thus rotate clockwise. When rotating, the upper wheel 2 and the central wheel 3 form together a pump unit with a pressure chamber 5, and in the same way the central wheel 3 and the lower wheel 4 function as another pump unit having a pressure chamber 6. Each of said pressure chambers 5, 6 is connected to a conduit 7 and 8, respectively, extending to the upper end of a vertical hydraulic cylinder 11 and 12, respectively, and each of said conduits is also provided with a restricted outlet 9 and 10, respectively, as known per so from regulator pumps previously used.

In the embodiment shown, the lower ends of the two cylinders 11, 12 are immersed in oil in a vessel 13. In the customary way, the cylinders have pistons 14, 15 with projecting rods 16 and 17, respectively, adapted to be connected to a valve member or another movable member which has to be controlled.

As known in the art, the supply of signal air to the pumps 2, 3 and 3, 4 is controlled by valves 18 and 19, respectively. In the embodiment shown, the movable valve members 20, 21, are suspended in bourdon pipes 22 and 23, respectively, and signal transmitting conduits 24, 25 connect the bourdon pipes to signal generating sources of pressure fluid. Two conduits 26 and 27 for supply of air extend from the valve housing 18 into the pump housing 1. The conduit 26 ends at the top of the periphery of the wheel 2, and the conduit 27 ends at the periphery of the central wheel 3 at a distance as great as possible before the pressure chamber 5 but at least two gear pitches from a minor suction chamber formed between the wheels 3 and 4. In a similar way, the other valve housing 19 is by means of conduits 28, 29 connected to the lower portion of the periphery of the wheel 4 and to the periphery of the central wheel 3 at a distance before the pressure chamber 6.

Liquid (oil) is supplied to the pump units by means of pipes 30, 31 having their inlet ends immersed in the oil in the vessel 13. Each of said pipes 30', 31 is divided into two branches 32, 33 and 34, 35, respectively, introduced through the Wall of the pump housing 1. Thus, the pipe 32 ends at the wheel 2 between the air inlet 26 and the pressure chamber 5, and the pipe 33 ends at the wheel 3 between the pressure chamber 5 and the air inlet 27. In the same way, the pipes 34, 35 end each on one side of the pressure chamber 6 inside of the air inlets 29 and 28, respectively. In fact, it has proved to be of great importance for the desired function that the empty spaces between the teeth are at first filled up with air. If the liquid were supplied at first, this incompressible medium would not permit a subsequent supply of air. As already indicated above, it is, moreover, a prerequisite that each inlet for gas and liquid is disposed at a distance of at least two gear pitches from the pressure chambers 5, 6 as well as from the central portions of the suction rooms located opposite thereto.

In the embodiment described above, the pump unit 2, 3 is thus fed with air and oil through the pipes 26, 27 and 32, 3-3, respectively, while the pump unit 3, 4 is fed correspondingly through the pipes 28, 29 and 34, 35. The two pump units operate quite independent of each other, and thus they can serve two different regulators each receiving signals from one of the conduits 24, 25. In the case the pump units are to be used for a single regulator, it may be necessary to arrange a valve mechanism which throttles and opens the air inlets alternately. Such a mechanism is described in the Swedish Patent No. 194,307, for instance, but the invention is, of course, not limited to any special mechanisms or regulators.

What I claim is:

1. A gear pump of the type which sucks liquid and gas to discharge a mixture thereof at its pressure side, said pressure side having a restricted outlet as well as an outlet pipe adapted to be connected to a hydraulic servo cylinder, comprising a housing, three gear wheels rotatably mounted therein, two of said wheels being in engagement with an intermediate central wheel to form two pump units each having an outlet from its pressure chamber, and inlets for gas and liquid on both sides of each pressure chamber at a distance of at least two gear pitches from the pressure chamber as well as from the central portion of the suc- 4 tion side, whereby the two pump units will operate independent on each other.

2. A gear pump as claimed in claim 1, in which each inlet for liquid is located between one of the pressure chambers and an inlet for gas.

References Cited UNITED STATES PATENTS 1,656,093 1/1928 Baker.

2,386,219 10/1945 Lauck.

3,119,339 1/1964 Clarke et a1. 1036 3,137,234 6/1964 Mosbacher 1032 3,242,867 3/ 1966 Mosbacher 103-2 3,266,430 8/1966 Mylo 103-6 3,267, 862 8/1966 Mosbacher 103--2 ROBERT M. WALKER, Primary Examiner.

WILBUR J. GOODLIN, Assistant Examiner.

U.S. C1. X.R. 

